/*
 *                  BioJava development code
 *
 * This code may be freely distributed and modified under the
 * terms of the GNU Lesser General Public Licence.  This should
 * be distributed with the code.  If you do not have a copy,
 * see:
 *
 *      http://www.gnu.org/copyleft/lesser.html
 *
 * Copyright for this code is held jointly by the individual
 * authors.  These should be listed in @author doc comments.
 *
 * For more information on the BioJava project and its aims,
 * or to join the biojava-l mailing list, visit the home page
 * at:
 *
 *      http://www.biojava.org/
 * 
 * Created on Apr 3, 2006
 *
 */
package org.biojava.services.das2;

public class SizeOf
{
    public static void main (String [] args) throws Exception
    {
        // Warm up all classes/methods we will use
        runGC ();
        usedMemory ();

        // Array to keep strong references to allocated objects
        final int count = 100000;
        Object [] objects = new Object [count];
        
        long heap1 = 0;

        // Allocate count+1 objects, discard the first one
        for (int i = -1; i < count; ++ i)
        {
            Object object = null;
            
            // Instantiate your data here and assign it to object
            
            object = new Object ();
            //object = new Integer (i);
            //object = new Long (i);
            //object = new String ();
            //object = new byte [128][1]
            
            if (i >= 0)
                objects [i] = object;
            else
            {
                object = null; // Discard the warm up object
                runGC ();
                heap1 = usedMemory (); // Take a before heap snapshot
            }
        }

        runGC ();
        long heap2 = usedMemory (); // Take an after heap snapshot:
        
        final int size = Math.round (((float)(heap2 - heap1))/count);
        System.out.println ("'before' heap: " + heap1 +
                            ", 'after' heap: " + heap2);
        System.out.println ("heap delta: " + (heap2 - heap1) +
            ", {" + objects [0].getClass () + "} size = " + size + " bytes");

        for (int i = 0; i < count; ++ i) objects [i] = null;
        objects = null;
    }

    public static void runGC () throws Exception
    {
        // It helps to call Runtime.gc()
        // using several method calls:
        for (int r = 0; r < 4; ++ r) _runGC ();
    }

    private static void _runGC () throws Exception
    {
        long usedMem1 = usedMemory (), usedMem2 = Long.MAX_VALUE;
        for (int i = 0; (usedMem1 < usedMem2) && (i < 500); ++ i)
        {
            s_runtime.runFinalization ();
            s_runtime.gc ();
            Thread.yield ();
           
            usedMem2 = usedMem1;
            usedMem1 = usedMemory ();
        }
    }

    public static long usedMemory ()
    {
        return s_runtime.totalMemory () - s_runtime.freeMemory ();
    }
    
    private static final Runtime s_runtime = Runtime.getRuntime ();

} // End of class